Trouble understanding change in tense

Question

The paragraph below began with the past tense but soon switched to present tense (highlighted in bold). I am trying to learn tense consistency. I don't know why such switch is allowed. It's very confusing for me to learn to keep a consistent tense =(

In Banjuh, the capital of Gambia, I met with a group of Gambians. They told me how for centuries the history of Africa has been preserved. In the older villages of the back country, there are old men called griots, who are in effect living archives. Such men memorize and, on special occasions, recite the cumulative histories of clans or families or villages as those histories have long been told. Since my forefather had said his name was Kin-tay (properly spelled Kinte), and since the Kinte clan was known in Gambia, the group of Gambians would see what they could do to help me. I was back in New York when a registered letter arrived from Gambia.

Word had been passed in the back country, and a griot of the Kinte clan had, indeed, been found. His name, the letter said, was Kebba Kanga Fofana. I returned to Gambia and organized a safari to locate him.

Answer 1

I'm assuming this is Alex Haley's "Roots"?

The tense shift is because he begins by telling a story about particular events that happened to him in the past, but shifts to describing a state of affairs that is current as of the telling of his narrative.

It wouldn't have been wrong to keep everything in the past tense, but it would inaccurately imply that the griots were strictly a historical phenomena.

It's a little subtle, but the key here is that he's shifting between two modes --storytelling and conveying information. The digression about the griots is as if he had included a bit of an encyclopedia entry in the book just so you would have some context for the story.

Answer 2

Yes. If you switch from storytelling mode, to narrative mode the tense may well change. You could for example employ past, present and future all in a single sentence if you said. 'I went to work at the zoo, where I feed the elephants daily, and where from next month I shall feed the tigers too.' The first verb 'went' is part of the account about your having gone to work that day, whereas 'feed' and 'will feed' provide a narrative about your life as a zoo employee.